This invention relates to underground worker protection and more particularly to high strength, light weight structural panels adapted for such use. This invention also relates to methods for preparing the structural panels, methods for assembling the panels and to excavation support systems formed therefrom. The installation, maintenance and repair of underground devices such as pipe, cable, valves, meters, amplifiers and the like require the excavation of a hole typically no larger than 8 feet long by 8 feet wide by 12 feet deep. However, the craftspersons performing the work of installing, maintaining and repairing these underground devices are constantly subjected to potential death and injury as a result of collapsing excavation walls.
Larger excavations remain open for long periods of time and are typically related to costly projects. For this type of excavation the cost of constructing some type of underground worker protection is a small percentage of the total project cost. In contrast, the type of excavations required for the installation, maintenance or repair of underground utility devices are relatively small, and the duration of the work being undertaken frequently is limited to a day or less. This makes the cost, handling and construction of underground worker protection in holes opened for utility work a significant part of the total project cost. As a consequence, without governmental enforcement, the natural result is to avoid their use.
The time and cost problems associated with the use of underground worker protection systems in smaller excavations opened for utility work include:
(1) The large variety of hole sizes, shapes, depths and soil types requiring worker protection;
(2) The inflexibility of available shoring products to accommodate a wide variety of hole sizes, shapes, depths and soil types.
(3) The inflexibility of available shoring products to efficiently accommodate multiple utility service lines coming into the same excavation at unpredictable angles and heights;
(4) The need to use shoring materials that have sufficient strength and structural integrity to withstand the horizontal and vertical pressures exerted on a cut wall or to withstand those produced by a collapsing wall;
(5) The fact that the standard materials currently used to provide the necessary strength (reinforced aluminum, steel, and thick cuts of wood) are heavy; and
(6) The products made of these materials require special handling equipment, are cumbersome, time consuming, inflexible and costly to use.
This invention seeks to resolve the problems of time, cost and worker safety when providing underground protection in holes excavated for the purpose of installing, maintaining or repairing some type of utility device such as pipe, cable, meters, valves, signal amplifiers, and the like.
Thus, the invention claimed herein relates to a high strength, light weight structural panel adapted to protect underground workers against the collapse of exposed walls in an excavation. This invention relates specifically to a structural composite panel which is to be used in a vertical plane and which is formed from a fiber reinforced resinous material which is fused or bonded to the exposed edge, top and bottom surfaces of a cellular core material, such as, but not limited to balsa wood, to provide a light weight monolithic composite of exceptionally high strength and load-bearing capacity. The invention also relates to methods for preparing such composites; methods for assembling such composites into an underground worker protection system; and excavation support systems formed therefrom.
U.S. Pat. No. 4,801,483, the disclosure of which is incorporated herein by reference, relates generally to the use of structural composites and, more particularly, to structural composites formed from a fiber reinforced resinous material that is fused to a cellular core material, to provide a light weight, monolithic composite panel of sufficient strength and load bearing capability to be used as a trench cover on road holes or openings where consistent, transient impact shock of the type occurring from the movement of vehicular traffic occurs.
End-grain balsa-core structural materials are widely used in transportation and handling equipment such as for floors of railroad cars, shipping containers, cargo pallets, and bulkheads, as well as in a variety of other similar load-bearing applications. These materials are also employed for structural insulation in aircraft applications, in housing and in boating. The use of structural composite materials, such as that claimed in U.S. Pat. No. 4,801,483, represents a unique use of such materials for withstanding impact shocks. Other balsa-core structural materials and methods for their preparation are described, for example, in U.S. Pat. Nos. 3,298,892 to Lippay, 3,325,037 to Kohn et. al., 4,271,649 to Belanger, and 4,343,846, the disclosures of which are incorporated herein by reference. Also related to balsa-core structures, and incorporated herein by reference, are U.S. Pat. Nos. 3,616,111 and 4,533,589.
There are a number of prior art patents dealing generally with shoring systems and underground worker protection. For example, U.S. Pat. No. 543,056 to Rue relates to the design and construction of a mechanical ditching jack of the type currently being used by underground construction workers. The invention being claimed in the present application proposes to eliminate the need for using such jacks, which are, at best, subject to the possibility of worker movement and collapse.
U.S. Pat. No. 3,224,201 to Brunton discloses an underground shoring system which requires, at a minimum, the use of vertical aluminum rails, aluminum cylinders and, under certain conditions, aluminum wales, all of which are heavy enough to require the use of mechanical lifting equipment for their placement. The Brunton system also requires the use of an external hydraulic system at the job site. Hydraulic shores, such as those disclosed in the Brunton patent, must be positioned every 4 feet on center against an excavation wall such that an 8 foot length would require three sets of shores. Under conditions of type C (OSHA classification) soils, hydraulic shores, such as those set forth in the Brunton patent, require the use of some type of sheeting material between the shores to prevent sloughing. OSHA requirements require this sheeting material to be either 1.125 in. plywood, 0.75 in. birch or 0.75 in. Finform. Moreover, the system described in the Brunton patent provides worker protection for only two opposite walls at any one time, the hydraulic shores disclosed in that patent can be used only where they can be positioned to exert pressure against the excavation wall.
The invention being claimed herein proposes to eliminate the need for using hydraulic shores of the type described in the Brunton patent and, therefore, the hydraulic systems that must accompany it to the job site as well as the need for other types of sheeting such as 1.125 in. plywood or 0.75 in. birch that must be used between shores in Type C soils. The present invention also offers the opportunity to span an area greater than the 4 feet without the use of vertical (soldiers) or horizontal (wales) members. The present invention can be used to provide underground worker protection without having to exert pressure against the walls of an excavation, and can provide four wall, as well as two wall, safety.
U.S. Pat. No. 3,335,573 to Ward relates to a safety lock used on hydraulic shoring such as that described in the abovediscussed Brunton patent. The Ward invention also utilizes a system of wales, which the present invention seeks to eliminate.
U.S. Pat. No. 3,381,483 to Huthsing relates to the construction of sea walls, docks and piers. The Huthsing invention relates specifically to the construction of a permanent structure and requires the use of steel I beams, steel reinforcing bar, concrete panels, and poured concrete to give it both strength and permanence (i.e., the Huthsing structure can not be constructed from light weight materials). In the Huthsing invention, the use of steel I beams, concrete panels and poured concrete require the use of heavy construction equipment such as cranes, pile drivers, cement mixers and flat bed trucks. The construction also requires the welding together of various members. The cost of the constructing the Huthsing permanent structures would be prohibitive in situations involving the maintenance, repair or installation of underground utility equipment such as pipe, cable, meters, valves, or amplifiers. The time required for the construction would prevent its use as a temporary underground worker protection system when installing, repairing or maintaining such things as pipe, cable, meters, valves, amplifiers, etc.. The construction would not be responsive to an emergency situation in terms of either time or manpower. Furthermore, the Huthsing patent does not describe an underground construction.
The present invention eliminates the need for heavy or special construction equipment such as cranes, pile drivers, cement mixers and flat bed trucks. The present invention also eliminates the need for utilizing more than two persons for its construction. Because of its light weight, ease of transport and construction, the protection system of the present invention is highly effective for emergency repair situations. The present invention is portable in that it can be easily carried from job site to job site without special equipment and manpower. Thus, the present invention has the versatility of being used as either a portable or permanent structure.
U.S. Pat. No. 3,420,065 to Holl deals with a shoring system that comprises vertically driven beams, or pilings, and planking. The Holl's shoring system requires some type of cross-bracing or wale system between vertical members and replaces a fixed length system of wooden wales and cross-members. The Holl's invention is for use in a wood shoring system customized by cutting timbers and constructing the shoring system in a hole at a job site.
The present invention is intended to eliminate the use of wales, or cross-members, in a shoring system; and is intended to eliminate the need for the wood or steel construction of a shoring system at the job site. The present invention also eliminates the need for driving steel beams or pilings when constructing a shoring system. The shoring system of the present invention comprises, in one aspect thereof, for a portable worker protection system that can be installed quickly and without heavy construction.
U.S. Pat. No. 3,802,205 to Dickinson relates specifically to a sea wall structure made of steel pilings, steel reinforced concrete block and metal support cables. Although the Dickinson invention utilizes pre-cast concrete parts, these parts must be customized to meet the requirements of the sea wall being constructed. The Dickinson invention requires the use of steel I beams, steel reinforcing bar, concrete panels, poured concrete and pre-tensioned, metal, support cable to give it both strength and permanence. The Dickinson invention refers specifically to the construction of a permanent structure and requires the use of heavy construction equipment such as cranes, pile drivers, cement mixers and flat bed trucks for its construction. Accordingly, the construction contemplated by the Dickinson patent requires the use of more than two people, thereby resulting in a cost of construction that would be prohibitive in situations involving the maintenance, repair or installation of underground utility equipment such as pipe, cable, meters, valves, or amplifiers. Furthermore, the time of construction of the Dickinson invention prevents its use as an underground worker protection system when installing, repairing or maintaining such things as pipe, cable, meters, valves, amplifiers, etc. Moreover, the construction of the Dickinson invention would not be responsive to an emergency situation in terms of either time or manpower. The Dickinson invention does not describe an underground construction.
The present invention eliminates the need for heavy or special construction equipment such as cranes, pile drivers, cement mixers and flat bed trucks; and because of the light weight materials that are used, the protection systems of the present invention can be constructed and handled by as few as two workers. The protection systems of the present invention are highly effective for emergency repair situations and can be transported easily from job site to job site without special equipment and manpower. The protection systems of the present invention are versatile and can be used either as a portable or permanent structure. The system of the present invention are specifically for use as an underground structure.
U.S. Pat. No. 3,864,921 to Marx relates to a shoring system that requires the use of a rigid, outer wall, removed from an excavated trench wall, a liner made of a resilient material for the excavated trench wall, and the filling of the space between the rigid wall and the lined trench wall with some type of gas or air filled envelopes. The Marx system generally is not applicable to the system of the present invention, except perhaps in the use of a mechanical, adjusting cross-member (strut) used to hold the fabricated walls upright and pressed against the excavated trench walls. The use of such a cross-member to support wood and steel materials is accepted practice. However, the present invention generally does not require such a support.
U.S. Pat. No. 3,937,026 to Kring discloses the on-site construction of aluminum, or steel, reinforced panels using a carrier, multiple support members, and two aluminum, or steel, component plates between which the support members are positioned. The Kring invention provides for a friction reducing method of disassembly.
The Kring structure is stationary and requires the use of a foot plate that is pointed and, with pressure, secured into the earth. The Kring structure can be used only by means of expanding support devices that press the reinforced panels against a trench wall, and requires the use of carrier frames so that, by inserting two component plates, its reinforced panels have sufficient thickness and strength to provide appropriate trench safety. The Kring structure requires multiple panels to provide a strength adequate to withstand soil pressures that would result from collapsing excavation walls. In addition, the Kring structure can not be transported to the job site in a crew truck, requires the use of heavy equipment for installation, and is not practical for use in excavations that can be opened and closed in the same working day.
U.S. Pat. No. 4,685,837 to Cicanese discloses an underground form system that requires the use of at least two panels placed side-by-side to form a wall of any size, wherein the panels are joined at their vertical sides by rigid members. In the Cicanese invention an open area for the entrance or exit of such things as pipe or cable must be obtained by cutting or otherwise fashioning the panels, attaching vertical members that support the two original panels and provide a slide for a smaller third panel that acts as a lift door. In the Cicanese invention the panels cannot fit on top of each other so that panel depth is limited by panel size. In the Cicanese invention the Pit Form System is stationary and horizontal brace bars or wales are required to make the entire system rigid and stable.
U.S. Pat. No. 4,917,543 to Cole relates to a wall system that employs a series of extruded polymeric materials, such as PVC, convex in shape and joined together by a system of wales. The Cole invention is intended primarily for use as a sound barrier, or a sea or retaining wall. The Cole wall system has, basically, three configurations, but requires the use of wales and poured concrete for its strength. Without the use of wales and concrete, the Cole wall system becomes essentially a sound barrier. The panels of the wall system must be a series of equally convex shapes. The Cole invention requires the use of a revetment system and is for a permanent, stationary wall structure.